With the rapid advance of network technologies and diversification of digital content (e.g. music, video, game, software, and document), the use of digital content has become increasingly popular. This tendency has raised concerns about protecting digital content and managing technology for preventing illegal copying and redistribution of paid digital content.
For example, the High-bandwidth Digital Content Protection (HDCP) is a technology designed to prevent illegal duplication of video data transferred through Digital Visual Interface (DVI). An HDCP-enabled device may be capable of encrypting and decrypting video data for playback of high quality content in compliance with HDCP protocol.
HDCP technology has recently evolved so as to be adopted to all bidirectional communication including wireless and compressed transmission independently of other interface standards such as DVI, High-Definition Multimedia Interface (HDMI), and DisplayPort. The HDCP technology includes a locality check protocol for restricting the receipt of the digital content to devices within a predetermined radius. However, since the locality check protocol establishes communication with any device that sends a response signal within a predetermined time, digital content may be transmitted to a device not intended to receive the digital content.